SAN DIEGO, Dec. 12, 2011 /PRNewswire/ -- Optimer Pharmaceuticals, Inc. (NASDAQ: OPTR) and Astellas Pharma Europe Ltd., a European subsidiary of Tokyo-based Astellas Pharma Inc. (Tokyo: 4503) announced today that the European Commission has granted Marketing Authorization (MA) for DIFICLIR (fidaxomicin) tablets for the treatment of adults with Clostridium difficile infections (CDI) also known as Clostridium difficile-associated diarrhea (CDAD). CDI is a significant problem in hospitals and long-term care facilities all over the world. EMA approval was based on two large, multi-national, Phase 3 clinical trials that demonstrated that DIFICLIR was as effective as oral vancomycin in treating CDI. DIFICLIR had a significantly lower rate of recurrence (including relapses) compared to vancomycin in the 30 days following treatment. DIFICLIR is the only drug approved by the EMA proven to significantly lower the rate of recurrence of CDI compared to oral vancomycin. The clinical trials included patients over the age of 65 and those taking concomitant antibiotics to treat multiple infections.

"The European approval is a key step in making fidaxomicin more widely available to patients across the globe to treat this very serious disease," said Pedro Lichtinger, President and Chief Executive Officer of Optimer. "We believe we have obtained a very strong label recognizing the benefits of DIFICLIR versus vancomycin, including significant reductions in recurrence."

The European approval affirms the recent positive opinion from the Committee of Medicinal Products for Human Use (CHMP) and is based on two Phase 3 clinical trials that were conducted to ensure the safety and efficacy of 400mg/day DIFICLIR (fidaxomicin) tablets compared to 500mg/day oral vancomycin for 10 days in subjects with CDI. The first Phase 3 study was carried out in 629 subjects in North America (US and Canada). The second Phase 3 study was carried out in 535 subjects in North America and Europe. Of the subjects enrolled in these studies, 47.9% were 65 years or older and 27.5% were treated with concomitant antibiotics. Both studies met their primary endpoint of non-inferiority, demonstrating that the proportion of subjects in whom clinical cure was achieved at the end of 10 days was similar for both DIFICLIR and oral vancomycin. In both trials DIFICLIR proved to have a statistically significantly lower rate of recurrence of CDI as compared to oral vancomycin 30 days after the end of treatment. The most common treatment related adverse reactions were vomiting (1.2%), nausea (2.7%) and constipation (1.2%).

DIFICLIR is described in the EU label as a narrow spectrum antimicrobial drug with bactericidal activity against C. difficile and inhibitory activity against C. difficile sporulation in-vitro. Fidaxomicin, the active ingredient in DIFICLIR, is a member of a new class of antibacterials called macrocycles.

Astellas Pharma Europe Ltd. is Optimer's exclusive licensee to develop and commercialize DIFICLIR in Europe and additional countries in the Middle East, Africa and the Commonwealth of Independent States.

TheSummary of Product Characteristics, including the DIFICLIR product label, can be accessed directly from the EMA website at http://www.ema.europa.eu .

About CDI

Clostridium difficile infection (CDI) has become a significant medical problem in hospitals, long-term care facilities and in the community. CDI is a serious illness resulting from infection of the inner lining of the colon byC. difficile bacteria, which produce toxins that cause inflammation of the colon, severe diarrhea and, in the most serious cases, death. Patients typically develop CDI from the use of broad-spectrum antibiotics that disrupt normal gastrointestinal (gut) flora, possibly allowing C. difficile bacteria to flourish. Older patients in particular are at risk for CDI, potentially because of a weakened immune system or the presence of underlying disease. Approximately two-thirds of CDI patients are 65 years of age or older. Historically, approximately 20% to 30% of CDI patients who initially respond to treatment experience a clinical recurrence.

About Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc. is a global biopharmaceutical company focused on discovering, developing and commercializing innovative hospital specialty products that have a positive impact on society. Optimer developed and commercialized DIFICID® (fidaxomicin) tablets, an FDA-approved antibacterial drug for the treatment of adult patients with Clostridium difficile-associated diarrhea (CDAD). Optimer has also received marketing authorization for fidaxomicin tablets in the European Union under the trade name DIFICLIR. The company is seeking marketing authorization for fidaxomicin in Canada and it intends to seek marketing authorization in other parts of the world where C. difficile has emerged as a serious health problem, including Asia. Additional information can be found at http://www.optimerpharma.com.

Forward-Looking Statements

Statements included in this release that are not a description of historical facts are forward-looking statements, including without limitation statements related to the potential availability of DIFICLIR to patients, future activities conducted under the Astellas collaboration and license agreement, the potential benefits of the collaboration and license agreement, Optimer's potential receipt of milestone payments and the future incidence and costs of CDAD. Words such as "believes," "would," "anticipates," "plans," "expects," "may," "intend," "will," and similar expressions are intended to identify forward-looking statements. The inclusion of forward-looking statements should not be regarded as a representation by Optimer that any of its plans will be achieved. Actual results may differ materially from those set forth in this release due to the risks and uncertainties inherent in Astellas' and Optimer's businesses including, without limitation, risks relating to: whether Optimer or Astellas will be able to complete and submit additional applications for marketing approval of DIFICLIR and whether regulatory authorities will review or approve such applications, the implementation and continuation of the Astellas collaboration and license agreement, each party's performance of its respective obligations under the collaboration and license agreement, Astellas' ability to successfully commercialize DIFICLIR in the licensed territory, whether DIFICLIR will receive reimbursement from government authorities and other healthcare payors, whether healthcare professionals will prescribe DIFICLIR, the development of alternative treatments for or means of preventing CDAD and other risks detailed in Optimer's filings with the U.S. Securities and Exchange Commission.